The present invention relates to an industrial pump supplying water mainly a high-temperature water, such as a feed water pump used in a heat power plant, an atomic power plant and the like.
Conventionally, a mechanical seal or the like is used in a shaft seal apparatus for an industrial pump supplying the water, mainly the high-temperature water, such as a boiler feed water pump used in the heat power plant and an atomic reactor feed water pump used in the atomic power plant. Since the shaft seal apparatus reaches a high temperature at a time of operating the pump, the shaft seal apparatus prevents a reduction of a shaft seal performance by being cooled by a cooling water introduced from an outside of the pump.
Further, as a cooling method of the shaft seal apparatus, for example, as described in JP-A-7-305691, there is employed a method of cooling the shaft seal apparatus by forming a jacket chamber in a part of a casing and a part of a mechanical seal cover, or between the casing and the mechanical seal cover so as to surround the shaft seal apparatus, and injecting the cooling water into the jacket chamber from the outside of the pump.
On the other hand, as a method of forming the jacket chamber so as to surround the shaft seal apparatus, as described in JP-A-7-305691, there is a method, for example, shown in FIGS. 7 and 8, in addition to a method of closing an opening portion of the jacket chamber formed within the casing by the mechanical seal cover, a method of closing the jacket chamber formed within the mechanical seal cover by the casing, a method of forming the jacket chamber in a juncture portion between the casing and the mechanical seal cover, and the like.
In a structure of a cooling means shown in FIG. 7, a cooling chamber c is formed within a bracket b so as to surround a shaft seal apparatus a, and a cover d is firmly fixed to an opening portion of the cooling chamber c in a liquid tight manner by a means such as a welding or the like.
Further, in a structure of a cooling means shown in FIG. 8, a cooling chamber c is formed in a shaft seal case e of a shaft seal apparatus a, a bracket b provided around the shaft seal case e closes an opening portion of the cooling chamber c, and a packing, for example, an O-ring f or the like is interposed in a boundary surface between the shaft seal case e and the bracket b, for preventing a liquid leak.
However, as in a fluid machine described in JP-A-7-305691, in a structure in which the jacket chamber is formed in a part of the casing or the mechanical seal cover, and the cooling chamber c is formed within the bracket b as shown in FIG. 7, since a structure of a wooden mold for manufacturing a casting mold becomes complicated in the case of manufacturing the casing, the mechanical seal cover and the bracket b as a cast product, a cost of the wooden mold becomes expensive. Further, it is necessary to previously form an opening for getting out sand in the jacket chamber and the cooling chamber in the cast product using the casting mold.
Accordingly, it is necessary to close the opening portion of the jacket chamber by a part of the mechanical seal cover and the casing after casting (in the case of JP-A-7-305691), or seal the opening portion of the cooling chamber c by the cover d (in the case of the cooling means shown in FIG. 7). As a result, the structure of the cooling means becomes complicated, and a cost of an entire pump is increased.
Further, since a defect such as a blow hole or the like tends to be generated in the casting at a time of casting, the casting lacks of a reliability. Further, in the case that the cover d is welded to the opening portion of the cooling chamber c, it is necessary to execute a work of forming a concave step portion in the opening portion of the cooling chamber c in accordance with a machine work, welding the cover d in a state of fitting the cover d to the concave step portion, and thereafter applying a heat treatment for removing a residual stress of the weld portion. Accordingly, a lot of work man hour is necessary for the machine work and the weld work, and a cost of an entire pump is increased.
On the other hand, as shown in JP-A-7-305691 and FIG. 8, in the structure in which the cooling chamber c is formed in the boundary portion between the casing and the mechanical seal cover or the boundary portion between the shaft seal case e and the bracket b, the O-ring f is provided for preventing the liquid leak from the boundary surface, however, since the O-ring f is deteriorated by the use under the high temperature and the seal effect is lowered at an early stage, it is necessary to periodically replace the O-ring.
However, it is necessary to execute the replacing work of the O-ring f by dissembling the shaft seal apparatus a, a lot of time and man hour are required for the replacing work and a workability is bad. Further, since the pump can not be operated during a repair period, it is necessary to stop the plant.